1. Field of the Invention
The present invention relates to a method of and an apparatus for automatically adjusting the characteristics of a dielectric filter.
2. Description of the Related Art
Typical dielectric filters are composed of electromagnetically coupled dielectric resonators. Each resonator is formed by a dielectric with an electrode film on it.
In order to obtain a dielectric filter having desired characteristics, a method has been used in which some electrode portions or some dielectric portions are cut so as to be removed, and/or alternatively some adjustment screws are driven so as to insert or remove some dielectric members or some metal members, thereby effecting a desired characteristic adjustment.
If physical properties of the materials forming a dielectric filter are made constant and if sizes of various portions of the dielectric filter are maintained with extremely high precision, it will be allowed to obtain substantially constant characteristics all the time. However, since there are in fact some irregularities in these characteristics, such irregularities should be taken into account in the actual design process. For example, a method has been in practical use in which when a resonance frequency is to be determined, an initial resonance frequency is designed so that it is always slightly below a desired resonance frequency, and some dielectric portions are cut and removed until the resonance frequency becomes the desired resonance frequency.
However, because perturbations caused by the cutting or adding or the insertion or removal of a dielectric material or an electrically conductive material in certain adjustment positions for adjusting the above-mentioned characteristics, a characteristic change of an object being adjusted is not necessarily linear. For this reason, the characteristic adjustment has been carried out manually, utilizing the experience and feeling of a human worker. This however, results in a problem, namely that productivity is low and it is impossible to carry out a constantly stabilized manufacturing process.
To cope with the above problem, Japanese Patent No. 2740925 discloses an automation capable of automatically adjusting the characteristics of the above-discussed electronic parts. This disclosure requires that when a characteristic variation relationship is calculated with respect to an adjusting amount at portions for characteristic adjusting so as to calculate only an adjusting amount for obtaining a predetermined characteristic in accordance with the above relationship, it is necessary to eliminate a problem called defective adjustment, which is caused due to a fact that the curves of characteristic variations will be different from one another corresponding to adjusting amounts of various products. For this reason, it is needed to obtain actual data by trimming the number of predetermined samples and it is also required to successively renew the trimming conditions with respect to the electronic parts of the predetermined numbers of samples, thereby dealing with an irregularity problem that occurs among respective lots of electronic parts and in respective manufacturing processes.
In order to provide a dielectric filter formed by a plurality of dielectric resonators and/or a combined input/output device such as a duplexer, a multiple mode dielectric resonator has been used, in order that the filter may be made light in weight and compact in size. For example, when a cross-shaped dielectric column is used so as to make use of a double mode or a triple mode, some predetermined portions of the above dielectric column have to be cut off so as to adjust the resonance frequency of each resonator. However, with a plurality of resonance modes, it is impossible to adjust the resonance frequency of one resonator (which may be referred to as an adjustment object) completely independently of other resonators. For instance, if certain portions of the dielectric column are cut off, the resonance frequencies of several resonance modes will be undesirably changed at the same time. There is only a ratio difference, which determines which resonance mode receives the largest influence. For this reason, in a case when it is required to adjust the characteristics of a dielectric filter employing several triple mode resonators, it is no longer substantially possible to use a method in which a human operator is allowed to perform the adjustment while at the same time adjusting the characteristics of the filter with a network analyzer.
To address these problems, the present invention provides a method and an apparatus for automatically and exactly adjusting the characteristics of a dielectric filter within a reduced time period.
One embodiment of the method invention comprises: an electric parameter extracting step including measuring characteristic parameters of a dielectric filter whose characteristics are to be adjusted, and thus calculating electric parameters of a designed equivalent circuit of the filter with the use of the characteristic parameters; an adjustment function generating step including adjusting electric parameter adjusting portions of the dielectric filter, thus generating, with the use of the electric parameters, advantageously obtained by an electric parameter extracting, device and with the use of an adjusting amount, adjustment functions indicating a variation amount of the electric parameters with respect to the adjusting amount; an adjusting amount calculating step for calculating the adjusting amount, in accordance with simultaneous equations involving the adjustment functions, with the use of electric parameters obtained before the adjustment and with the use of desired electric parameters; and an adjusting step for adjusting an amount calculated in the adjusting amount calculating step, further, the electric parameter extracting step and the adjusting amount calculating step and the adjusting step are repeatedly carried out until the characteristic parameters of the dielectric filter arrive at predetermined values.
In the adjusting amount calculating step, an adjusting amount is calculated by multiplying a calculation result with a predetermined ratio, the calculation result being obtained by incorporating into the simultaneous equations involving the adjustment functions, the electric parameters obtained in the electric parameter extracting step and the desired electric parameters.
In this way, in accordance with the simultaneous equations involving adjustment functions, the characteristic parameters (S parameters) of the dielectric filter are measured, the adjusting amounts of electric parameter adjusting portions are calculated with the use of a difference between electric parameters of a designed equivalent circuit of the filter calculated from the characteristic parameters and the desired electric parameters. By repeatedly correcting the calculated adjusting amounts until the characteristic parameters of the dielectric filter arrive at predetermined values, it is possible to exactly and automatically adjust the characteristics of a dielectric filter without depending upon the experience and feelings of a human operator as in conventional methods.
A further embodiment of the invention relates to apparatus for carrying out the methods described herein.
Other aspects, features and advantages of the invention will become apparent from the following.